Aircraft, notably jet aircraft, have turbojet engines which are significant sources of noise emissions.
In order to attenuate the emissions of noise coming from the turbojet engines, the nacelles of these turbojet engines are fitted with acoustic panels that line the internal wall of the nacelles in the region of the air intakes.
In general, these acoustic panels have a structure of sandwich type. They are usually shaped in a mold to give them a shape suitable for the nacelle to which they are to be fitted. These panels comprise one or several layers of cellular structure of the honeycomb type able to trap noise. This layer of cellular structure has an external face covered by a porous layer, referred to as the facesheet, and an internal face covered with an impermeable layer referred to as the backplate.
At the present time, the facesheet used for acoustic panels is manufactured using lengthy and complex processes. For example, the facesheet may be manufactured from facesheet strips welded together. After assembly, these facesheet strips require a full manual inspection in order to assess their quality. The facesheet strips are then welded together to cover the mold that shapes the acoustic panel. By way of example, the facesheet needs to cover an area of approximately 12 m2 of a mold intended for a nacelle of an aircraft of the A380 type. The method of manufacturing the facesheet is therefore lengthy, complex and expensive to implement.
There are alternatives whereby facesheets are manufactured from perforated layers. The perforating may be done before or after the layers of the acoustic panel are assembled. However, the step of perforating these layers generates a significant waste of material of which these layers are made. The perforation step may also weaken the structure of the material of which these layers are made.